1. Field of the Disclosure
The present disclosure relates to an organic light emitting diode display apparatus and a method for driving the organic light emitting diode display apparatus.
2. Description of the Prior Art
An Organic Light Emitting Diode (OLED) display apparatus coming into the spotlight as a display apparatus has advantages of a fast response speed, high light emitting efficiency, high luminance and a wide viewing angle because of using an OLED which emits light by itself.
The OLED display apparatus is divided into a passive matrix type, an active matrix type and so on, according to a driving manner.
Among these, in the active matrix type OLED display apparatus, a scan signal, a data signal, a driving power and so on are provided to a plurality of pixels disposed in a matrix shape, a selected pixel emits light, and thus an image may be displayed.
A driving method of the OLED display apparatus for displaying the image includes a voltage driving manner, a current driving manner, a digital driving manner, etc. Among these manners, the digital driving manner displays one frame grayscale with a plurality of sub-frames. For example, in case of displaying the image with 32 grayscales, the one frame may be divided into five sub-frames. The OLED display apparatus sets a weighted value (e.g a binary weight) of a corresponding sub-frame by controlling a light-emitting period in each of the sub-frames. For example, the OLED display apparatus sets each of the sub-frames so that the weighted values of each of the sub-frames are 1, 2, 4, 8 and 16 according to an antilogarithm of 2, after the manner of setting the weighted value of a first sub-frame as 1 and setting the weighted value of a first sub-frame next to the first sub-frame as 2. The OLED display apparatus displays the one frame grayscale by combining the sub-frames of which the weighted value is differently set according to the light-emitting period.
In the digital driving manner, the sub-frame may be divided into a writing period and the light-emitting period. The OLED display apparatus selects a scan line in the writing period and provides the driving power to pixels of the selected scan lines. At this time, a length of the writing period may be fixed, but a length of the light-emitting period is differently set according to the weighted values of each of the sub-frames. For example, the length of the light-emitting period of the sub-frame of which the weighted value is four is four times of the length of the light-emitting period of the sub-frame of which the weighted value is one.
Among the light-emitting periods having different lengths, the length of the light-emitting period may be shorter than the length of the writing period. For example, when the length of the writing period is 2 unit times and the length of the light-emitting period in the sub-frame of which the weighted value is 4 is 2 unit times, the length of the light-emitting period in the sub-frame of which the weighted value is 2 is 1 unit time, and the length of the light-emitting period in the sub-frame of which the weighted value is 1 is 0.5 unit time. At this time, the length of the light-emitting period in the sub-frame of which the weighted value is 2 and the length of the light-emitting period in the sub-frame of which the weighted value is 1 are shorter than the length of the writing period (it is assumed that the length of the writing period is fixed to 2 unit times).
In a specific sub-frame, when the length of the light-emitting period is shorter than the length of the writing period, a non-light-emitting period is generated in the corresponding sub-frame. The OLED display apparatus selects the scan lines one by one in the writing period. Therefore, although the light-emitting period of a corresponding scan line is finished, the OLED display apparatus becomes a non-light-emitting state wherein the OLED display apparatus cannot emit light until the writing period with respect to all scan lines is ended.
Since one frame time is finite, it is necessary to minimize the length of the non-light-emitting period, and to optimize the lengths of the light-emitting period and the writing period.